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Here is an example for this change.
$ sudo perf record -e 'ftrace:function' --filter='ip==schedule'
$ sudo perf report
The output of perf before this patch:
\# Samples: 100 of event 'ftrace:function'
\# Event count (approx.): 100
\#
\# Overhead Trace output
\# ........ ......................................
\#
51.00% ffffffff81f6aaa0 <-- ffffffff81158e8d
29.00% ffffffff81f6aaa0 <-- ffffffff8116ccb2
8.00% ffffffff81f6aaa0 <-- ffffffff81f6f2ed
4.00% ffffffff81f6aaa0 <-- ffffffff811628db
4.00% ffffffff81f6aaa0 <-- ffffffff81f6ec5b
2.00% ffffffff81f6aaa0 <-- ffffffff81f6f21a
1.00% ffffffff81f6aaa0 <-- ffffffff811b04af
1.00% ffffffff81f6aaa0 <-- ffffffff8143ce17
After this patch:
\# Samples: 36 of event 'ftrace:function'
\# Event count (approx.): 36
\#
\# Overhead Trace output
\# ........ ............................................
\#
38.89% schedule <-- schedule_hrtimeout_range_clock
27.78% schedule <-- worker_thread
13.89% schedule <-- schedule_timeout
11.11% schedule <-- smpboot_thread_fn
5.56% schedule <-- rcu_gp_kthread
2.78% schedule <-- exit_to_usermode_loop
Link: http://lkml.kernel.org/r/20190209161919.32350-1-changbin.du@gmail.com
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.